This application is directed in general to the design and manufacture of an X-ray detector and an X-ray detector formed thereby. Specifically, this application is directed to the design and manufacture of flat panel X-ray detectors and the flat panel X-ray detectors formed thereby, which in turn may be used in medical imaging systems, devices or other apparatus for example.
It should be appreciated that engineering and manufacturing flat panels adapted to be used in X-ray detectors for example, is a complex endeavor. Solid state X-ray imaging technology has steadily advanced due in part to the development of photo sensitive semiconductor arrays using either indirect X-ray-to-light scintillation panels (Amorphous Silicon with CsI for example) or direct X-ray conversion panels (Amorphous SE, PbO or Hgl for example). It is contemplated that one or more of those technologies may use transistor switches (TFT-FETs for example) providing effective multiplexing of a pixel array, enabling board analog-digital conversion to be performed using a smaller number of converters in comparison to the total number of converters than the total number of pixels in a given X-ray detector panel.
It is further contemplated that one or more of these technologies may use deposited metal lines (conduction paths formed by sputtering Mo, Al, Cu or other conductor metals for example) forming data and scan lines in a grid of rows and columns, facilitating the control of the TFTs (in one direction) while carrying a charge from the photo elements (in a different or opposing direction). As the X-ray detector panel pixel sizes decrease, and panel sizes increase, the ratio of signal (charge) to path length from photo sensor to the A/D converter dramatically decreases. This phenomenon is found to be true for both X-ray and CT detectors.
At the same time, in order to handle the smaller and lengthier data line paths and still produce acceptable image quality, the design of the A/D conversion system has become increasingly complex. It is contemplated that, in order to produce acceptable Signal to Noise Ration (“SNR”), noise levels well below about 2000 electrons are not uncommon in these types of systems. However, such complex solid state systems have become inherently more susceptible to electric and/or magnetic (referred to as Electro-Magnetic or “EM”) noise induced onto the photo sensor panel (induced primarily onto the data line paths).
Effectively shielding high frequency, Electro-Magnetic noise has been shown to be feasible, but not without some level of X-ray photon attenuation into the X-ray sensitive surface of the detector. Effective shielding of low and high frequency, Electro-Magnetic noise is not possible using current materials, as low frequency magnetic fields require metallic elements which greatly attenuate X-ray photons in medical applications. For example, EM noise has been shown to be at sufficient levels to effect images within certain solid state X-ray systems which are in close proximity to organ and catheter navigational systems, pace maker placement and programming systems, magnetic catheter drive systems as well as RF ablation systems. These types of systems may cause electric and/or magnetic or EM field strengths well in excess of those required for susceptibility testing as part of the international certification.